Crystal structures at low temperatures of Sb(CH3)5 (a = 663.0(2), b = 1100.4(3), c = 1109.0(3) pm; Z = 4; Ccmm), Sb(C6H5)3(CH3)2 (a = 1527.9(2), b = 791.2(1), c = 1781.7(3) pm; beta = 104.59(1)degrees; Z = 4; P2(1)/c, and Li+(THF)(4)Sb(CH3)6- (a = 1785.7(6), b = 852.5(3), c = 1261.7(5) pm; beta = 134.74(4)degrees; Z = 2; C2/m) are presented and compared with those of recently prepared Bi(CH3)(5) and Li+(THF)(4)Bi(CH3)(6)(-). All pentacoordinated compounds have very regular trigonal bipyramidal structures, in contrast to Sb(C6H5)(5) and Bi(C6H5)(5). Differences between axial and equatorial bond lengths are,pronounced in antimony compounds, but not so in violet Bi(CH3)(5). Colorless Li(THF)(4)Sb-+(CH3)(6)(-) and orange Li(THF)(4)Bi-+(CH3)(6)(-) have octahedral anions, with averaged bond lengths of 223.5(5) pm (Sb-C) and 233(1) pm (Bi-C).